The present invention relates to an optical switch using carrier injection so as to utilize refractive index change and/or absorption coefficient change caused thereby, and particularly it relates to an optical switch conducting high-speed operations, having an element small in size and being suitable for an optical integrated circuit.
Among the prior-art optical switches using carrier injection, there is a total internal reflection type (TIR) optical switch as an optical stitch which alters its output ports by utilizing the refractive index change, on which descriptions are made in the Collected Papers S7-4 for the 1985 National Meeting of Semiconductor-Material Department of Institute of Electronic Communication Engineer of Japan, INOUE et al., and in Pending U.S. patent application Ser. No. 684,784 (MATSUMURA et al.). Moreover, there is a loss modulation type optical switch as an optical switch which acts as an intensity modulator and/or an ON/OFF switch by utilizing the absorption coefficient change, among the prior-art switches, on which a description is made in the Collected Papers 926 for the 1985 Combined National Meeting of Institute of Electronic Communication Engineers of Japan, YAMAGUCHI et al. These optical switches utilize a large refractive index change and/or absorption coefficient change caused by the injection of carriers, and they are characterized by being small in size and having a high extinction ratio. In these optical switches, however, the carriers injected in a switching region implementing alteration of output ports and/or action as an intensity modulator and/or an ON-OFF switch become extinct in accordance with the life time of their recombination when the optical switches are desired to turn OFF, in other words, when the injection of the carriers is stopped. Consequently, the response speed of the switches is limited to be about several nsec to several tens nsec.